Tablets containing a Kampo medicinal extract powder (hereinafter also be referred to as “extract powder”) are generally manufactured by a direct powder-tabletting process in which a powder mixture of a tablet composition containing a extract powder is directly tabletted to yield tablets; or by a tabletting process in which a granulated substance having a small diameter and containing a extract powder is formed, and a powder mixture of a tablet composition containing the granulated substance is then tabletted to yield tablets.
Such Kampo medicinal extract powders are highly water-absorbable, and the tablets are preferably manufactured by a manufacturing method that does not require addition of water, typically from the viewpoint of handleability in manufacturing. Accordingly, tablets containing a Kampo medicinal extract have often been manufactured by the direct powder-tabletting process in which a powder mixture is directly tabletted.
In these tablets manufactured by the direct powder tabletting process, however, the Kampo medicinal extract powder is bound firmly, water does not permeate satisfactorily and a general disintegrator with swelling property does not work effectively. It takes a long time for the tablets to disintegrate and the active ingredients do not dissolve satisfactorily. Thus, tablets superb in practical use have not yet been obtained.
To solve this problem, attempts have been made, for example, to reduce the content of the extract powder in the tablets or to add large quantities of, for example, a vehicle (excipient), a disintegrator and/or a binder. However, these techniques invite tablets with larger sizes or higher manufacturing cost due to expensive disintegrators. Certain tablets comprising sodium hydrogen carbonate so as to improve dissolution properties are known, but they do not yet show sufficient advantages.
In the process of making tablets via a granulated substance, the granulated substances containing a Kampo medicinal extract powder is manufactured typically by dry pulverization-granulation, wet extrusion-granulation or fluidized-bed granulation. However, the Kampo medicinal extract powder is highly water-absorbable as described above, and extract powder becomes firmly bound and often forms large aggregates when water is added in these processes. Therefore, the manufacturing of granulated substance requires sophisticated techniques typically to control the amount and rate of the addition of water precisely and facilities therefor. In addition, the wet extrusion granulation carries a problem of a residual solvent in final preparation products, because this technique uses an organic solvent such as ethanol. The fluidized-bed granulation invites a longer manufacturing time period, because the water content of the granulated substance must be controlled within a narrow range during granulation.
Accordingly, an object of the present invention is to solve the above problems, to improve the disintegration and dissolution properties of tablets containing a Kampo medicinal extract powder and to provide a tablet composition containing a Kampo medicinal extract which can be disintegrated and dissolved satisfactorily, and a process for manufacturing the same.